Interpretive Summary: For centuries, cotton fabrics have always been woven by sizing or coating the cotton singles warp yarns with a suitable adhesive, such as starch, carboxy methyl cellulose (CMC), or polyvinyl alcohol, etc., in order to increase breaking strength and abrasion resistance of the yarns and, hence, to achieve efficient weaving. However, warp sizing and the subsequent fabric desizing are costly, complex and, more importantly, environment-sensitive processes. Based on recommendation of cotton textile industry, the Agricultural Research Service, USDA, initiated research to explore feasibility of reducing or preferably eliminating the warp sizing. Preliminary research investigations at least have revealed the mechanical feasibility of size-free weaving of cotton fabrics. However, the fabric quality is not yet satisfactory and shows numerous, tiny defects. Besides other factors, the yarn abrasion in weaving is a complex function of the yarn structure, tension and friction. This research comprehensively investigated the real-time dynamic tensions of single strands of the warp, in order to have a better understanding of the fabric defects. The results show that the yarn tension and friction during weaving indeed are the critical factors in controlling the yarn abrasion and hence fabric defects.

Technical Abstract:
A 100% cotton, size-less common warp was used to study the real-time tensions of single strands of the warp during weaving on a high-speed weaving machine. The machine was operated under almost mill-like conditions. In order to investigate the independent effects of the weaving speed and fabric construction on the tension behavior/fluctuations of individual warp yarns, the speed was varied, in steps, from 250 to 550 picks (the machine’s maximum speed possible) per minute and the pick density was varied from 20 to 50 picks per inch, while maintaining the same ½-twill weave structure. Analyses of the single-strand (SS) real-time, dynamic tensions computed online revealed: (1) tension fluctuations within a weaving cycle of 360 degrees; (2) tension variations among different strands of the warp; and (3) overall tension variations and fluctuations caused by the different weaving speeds and fabric constructions (pick densities). Results showed that the SS tension varied from a minimum 20 g (when the shed was level) to almost 100g at the (beat-up) peak. Further, the tension variations among different strands in the body of the warp were not significant, showing that the original, inherited “virgin” tensions of the warp yarns on the loom beam were uniform and consistent. Furthermore, the dynamic yarn tensions were considerably influenced by the basic (set) ground warp tension (~100 kgf) and the pick density. The weaving speed did not have much influence either on the absolute tension value or on its fluctuations within a weaving cycle. This manuscript describes the test results, along with the experimental set-up that included a state-of-the-art yarn tension meter, computer and accessories, and the various on-line yarn tension graphs obtained.